Fine terminal, its manufacturing method, and contact sheet

ABSTRACT

A micro terminal for inspection or installation with high connection reliability is provided at lower cost. A micro terminal according to the present invention has electrical conduction between the micro terminal and an electrode of an electronic device or an inspection device and includes a columnar contactor in contact with the electrode. The contactor has a spring structure which is elastically deformed when pressed against the electrode. The contactor includes a protrusion protruding outwardly at its end in contact with the electrode and the shape of the protrusion has a part of a sphere or a part of a paraboloid of revolution.

RELATED APPLICATION

This application is a national phase of PCT/JP2004/018394 filed on Dec.9, 2004, which claims priority from Japanese Application No. 2003-414280filed on Dec. 12, 2003, the disclosures of which Applications areincorporated by reference herein. The benefit of the filing and prioritydates of the International and Japanese Applications is respectfullyrequested.

TECHNICAL FIELD

The present invention relates to a micro terminal that is pressedagainst an electrode of an electronic device including IC or LSI or thelike to obtain electrical conduction, and to a method of fabricating thesame. Further, the present invention relates to a contact sheet, aninspection device and an electronic device including the micro terminal.

BACKGROUND ART

For inspection of electrical conduction of an electronic deviceincluding IC or LSI or the like, a socket for inspection is used with aconnection terminal pressed against an electrode of the electric deviceto take out an electrical signal from the electrode through theconnection terminal. A connector for installation is used with aconnection terminal pressed against a land electrode of an electricdevice to maintain electrical conduction through the connectionterminal. The inspection socket and the installation connector areprovided with the number of connection terminals corresponding to thenumber of electrodes of an electronic device for connection. Aselectrodes of an electric device increase in density, the connectionterminals of the inspection socket and the installation connector arealso required to increase in density.

As the connection terminal, for example, a connection terminal for BGA(Ball Grid Array) is known which has a planar spiral shape beforeconnection to a ball-shaped electrode and, due to the connection to theball-shaped electrode, the spiral deforms in accordance with the shapeof the ball-shaped electrode (see Patent Document 1). The spiralterminal can address the densification of electrodes and has highconnection reliability since it can ensure electrical conduction inaccordance with the shape of a ball-shaped electrode.

A spiral terminal for inspection includes a volute terminal which has aspiral spring that is lower at its perimeter and higher toward itscentral portion, for example (see Patent Document 2). When a conicalprobe portion disposed at the end of the volute terminal is pressedagainst a planar electrode of a body to be inspected, it is ensured thatthe conical probe portion is connected to the planar electrode of thebody to be inspected due to urging force of the spring.

Patent Document 1: Japanese Patent Laying-Open No. 2002-175859

Patent Document 2: Japanese Patent Laying-Open No. 2001-235486

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The spiral terminal is fabricated by a mechanical processing method bywinding up a plate-shaped body, a method combining lithography usingultra-violet ray of a wavelength of approximately 200 nm and plating,laser processing, etching or punching, for example. When the spiralterminal is fabricated by mechanical processing by winding up aplate-shaped body, however, there is a limit in making the spiralterminal smaller and it is difficult to fabricate a precise terminalaccurately in large amount with excellent reproducibility. With a methodsuch as lithography using ultra-violet ray, laser processing orpunching, the aspect ratio is small since only a terminal of a thicknessof not more than approximately 20 μm can be obtained.

Due to the small aspect ratio, when a stroke (the amount of deflectionof a spring) is made larger to obtain a spiral terminal with highconnection reliability, the spring becomes thinner and cannot conductlarge current of at least 0.5 A. Further, due to the small aspect ratio,the number of spirals of the terminal becomes small. When the stroke ismade larger, the contact load becomes smaller, and when the contact loadis made larger, the stroke becomes smaller. Accordingly, only a microterminal with low connection reliability can be obtained.

When an electrode of a body to be connected is plate-shaped, it isnecessary for a connection terminal to have a convex structure to obtainhigh connection reliability. An additional process is required forprocessing into a convex structure after the spiral spring is formed,leading to reduced productivity and increased manufacturing cost. Inaddition, since it is not easy to process a micro spiral terminal into aconvex structure, manufacturing yield is reduced. When the connectionterminal is made conical with a sharp end and is pressed against aplanar electrode of a body to be connected, the electrode of the body tobe connected is likely to be damaged, since it is made of a softmaterial such as gold or solder. If the electrode is damaged in aninspection stage, the defect ratio in a subsequent installation stage ishigher, leading to lower connection reliability. On the other hand,since the end of the connection terminal also tends to be deformed,stable electrical connection cannot be obtained for repeated use of along period of time.

Since a conical protrusion structure can be formed only by mechanicalprocessing, sequent processing is necessary, leading to increasedmanufacturing cost. In addition, when the conical protrusion structureis formed by mechanical processing, variation in the product is severaltens of μm, causing variation in height, variation in stroke when incontact with an electrode, and variation in contact load, leading toreduced connection reliability.

One object of the present invention is to provide a micro terminal forinspection or installation with high connection reliability at reducedcost. Another object is to provide a contact sheet, an inspection deviceand an electronic device including the micro terminal.

MEANS FOR SOLVING THE PROBLEMS

A micro terminal according to the present invention has electricalconduction between the micro terminal and an electrode of an electronicdevice or an inspection device, characterized in that the micro terminalincludes a columnar contactor in contact with the electrode, and thecontactor has a spring structure which is elastically deformed by beingpressed against the electrode, and the contactor includes a protrusionprotruding outwardly at its end in contact with the electrode, and theshape of the protrusion has a part of a sphere or a part of a paraboloidof revolution.

Preferably, the contactor has a spiral spring structure or a structurein which a plurality of meandering springs are disposed from itsperimeter portion toward its central portion. Further, preferably, thecontactor has a structure in which its perimeter portion has a tubularring structure. Preferably, the micro terminal has a contactor at eachof opposing ends in contact with the electrode and the protrusion has aV-shaped groove opening toward the direction in which the protrusionprotrudes. Preferably, the micro terminal is formed of nickel or anickel alloy and has a coat layer including a precious metal or aprecious metal alloy or polytetrafluoroethylene gold.

A method of fabricating a micro terminal according to the presentinvention is characterized in that the contactor of the micro terminalis fabricated by a method including the steps of: forming a resin moldby X-ray lithography; forming a layer including a metal material at theresin mold on an electrically conductive substrate by electroforming;polishing or grinding; forming a resin mold on the layer including ametal material by lithography; electroforming a layer including a metalmaterial at the resin mold to form a protrusion protruding outwardly;removing the resin molds; and removing the electrically conductivesubstrate.

In another aspect, the method of fabricating the micro terminalaccording to the present invention is characterized in that thecontactor of the micro terminal is fabricated by a method including thesteps of: forming a resin mold by a metal mold; forming a layerincluding a metal material at the resin mold on an electricallyconductive substrate by electroforming; polishing or grinding; forming aresin mold on the layer including a metal material by lithography;electroforming a layer including a metal material at the resin mold toform a protrusion protruding outwardly; removing the resin molds; andremoving the electrically conductive substrate. Preferably, theprotrusion formed is provided with a V-shaped groove formed by cuttingwith a dicer.

A contact sheet according to the present invention includes theabove-described micro terminal, characterized in that the contact sheethas a hollow electrode penetrating the sheet in the thickness directionand a contactor on the hollow electrode and the hollow electrode has ahollow portion to accommodate the protrusion when the spring of thecontactor makes a stroke. Preferably, the contact sheet is formed byjoining the hollow electrode and the contactor by resistance welding.

An inspection device according to the present invention is characterizedin that the inspection device has a socket including the above-describedmicro terminal and is used to inspect semiconductor in land grid arrayarrangement. An electronic device according to the present invention ischaracterized in that the electronic device has a connector includingthe above-described micro terminal and is connected to a land electrode.

EFFECTS OF THE INVENTION

Due to high aspect ratio, the micro terminal according to the presentinvention has high connection reliability since a spring can be madethicker and the elastic energy of the spring can be made larger whilethe terminal is very small. With a fabricating method according to thepresent invention, a micro connection terminal can be providedprecisely, with high reproducibility and at reduced cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the structure of a contactor in a micro terminal accordingto the present invention.

FIG. 2 is a cross-sectional view of the contactor in the micro terminalaccording to the present invention when the contactor is cut in a planeperpendicular to the longitudinal direction.

FIG. 3 shows processes of a method of fabricating a socket forinspection according the present invention.

FIG. 4 shows processes of a method of fabricating the contactor in themicro terminal according to the present invention.

FIG. 5 shows processes of a method of fabricating the contactor in themicro terminal according to the present invention.

FIG. 6 is a cross-sectional view of the contactor in the micro terminalwhen the contactor is cut in a plane perpendicular to the longitudinaldirection.

FIG. 7 shows the structure of the contactor in the micro terminalaccording to the present invention.

FIG. 8 shows a method of forming a protrusion in the micro terminalaccording to the present invention.

FIG. 9 shows processes of a method of fabricating a contact sheetaccording to the present invention.

DESCRIPTION OF THE REFERENCE SIGNS

1 u: spring, 1 t: protrusion, 1 tc: contact surface of the protrusion,31, 91 a, 91 c: contactor, 32: substrate, 35: semiconductor, 38:transformer, 50: metal mold, 91: micro terminal, 91 b: hollow electrode

BEST MODES FOR CARRYING OUT THE INVENTION

(Micro Terminal)

A micro terminal according to the present invention includes a columnarcontactor in contact with an electrode and the contactor has a springstructure which is elastically deformed when pressed against theelectrode. The contactor includes a protrusion protruding outwardly atits end in contact with the electrode. The shape of the protrusion has apart of a sphere or a part of a paraboloid of revolution. FIG. 1 shows atypical example of the contactor. (a) is a perspective view, and (b) isa cross-sectional view when the contactor is cut in a plane passing thecenter and parallel to the longitudinal direction. FIG. 1 shows acontactor having a spiral spring structure. The contactor has a columnarspring 1 u and a protrusion 1 t protruding outwardly at the center 1 ucof a spiral of spring 1 u. Protrusion 1 t includes a contact surface 1tc in contact with an electrode of an electronic device or an inspectiondevice. Contact surface 1 tc has a shape of a part of a sphere or a partof a paraboloid of revolution.

FIG. 6 shows another contactor. The contactor shown in FIG. 6 has astructure in which a plurality of meandering springs are disposed fromthe perimeter portion toward the central portion of the contactor(hereinafter referred to as a “gimbal spring structure”). Since currentflows along the meandering springs in the spring shape, electromagneticfields generated cancel each other and excellent high frequency propertyis obtained. (a) in FIG. 6 shows a contactor of a round shape as a wholeand having three springs linked at the central portion. (b) shows acontactor of a square shape as a whole and having four springs linked atthe central portion. When the contactor is square as a whole, the areaoccupied by a spring on a contact sheet of a connector for installationor a socket for inspection is larger, leading to better springefficiency.

As with a conventional spiral terminal of a convex shape, when a microterminal with a sharp conical end is pressed against a planar electrodeor the like as a body to be connected, the terminal tends to bemechanically damaged and the end of the connection terminal is alsodeformed, lowering connection reliability. However, for the contactor inthe micro terminal according to the present invention, the shape ofprotrusion 1 t forms a part of a sphere or a part of a paraboloid ofrevolution, as shown in FIG. 1. Accordingly, an electrode of a body tobe connected is not mechanically damaged. Even when repeatedlyconnected, the contactor is less likely to have variation in heightbecause of the crushed end of the protrusion or lower stability ofelectrical connection because of change in the contact area. Even whenthe spiral terminal is obliquely connected to an electrode,predetermined connection condition can be maintained.

Preferably, a perimeter portion 1 ug of columnar spring 1 u has atubular ring structure. When perimeter portion 1 ug has a tubular ringstructure, installation to a substrate is easy and the micro terminalcan be grasped easily. Since the micro terminal can be grasped easily,it can be fixed firmly. Further, since there is no end of the spring atthe perimeter portion, a substrate is less likely to be cut away by anend of the spiral spring even when repeatedly connected to an electrode,leading to high stability.

In the contactor according to the present invention, as shown in FIG. 1,the outer diameter D is not more than 1 mm and the thickness b of spiralspring 1 u is 100–500 μm and the height c of protrusion 1 t is 50–200μm. Although FIG. 1 shows protrusion 1 t with a neck, a protrusionwithout a neck is also included in the present invention. Further, FIG.1 shows an example in which the cross section is almost circular whenthe contactor is cut in a plane perpendicular to the longitudinaldirection. However, the cross section may be not only circular but alsoelliptical or partly deformed circular or a polygon such as a triangleor a rectangle. The polygon includes not only a polygon with pieces ofthe same length but also with pieces of different length.

FIG. 2 shows an example in which the cross section is circular when thecontactor according to the present invention is cut in a planeperpendicular to the longitudinal direction. (a) is a cross sectionalview of a contactor with a spiral spring including one arm. (b) is across sectional view of a contactor with a spiral spring including twoarms. A spiral spring including at least three arms is also included inthe present invention. In the example of (b), the ends of the two armsare linked at the central portion and the linked portion has aprotrusion (not shown).

When the protrusion in the micro terminal has a V-shaped groove openingtoward the protruding direction of the protrusion as shown in FIG. 7,the crown-shaped protrusion surrounds and contacts a solder bump of asolder bump electrode of small height as a body to be connected,producing a sufficient stroke to cause a necessary load and breaking anoxide film of the surface of the solder bump by the edge of theprotrusion to obtain electrical conduction. Accordingly, excellentelectrical contact with the surface of the solder bump is provided.Singular V-shaped groove or a plurality of V-shaped grooves may beeffective, however, especially for the solder bump, grooves crossingorthogonally provide high connectivity.

FIG. 3( d) shows an example of a socket for inspection including themicro terminal according to the present invention. As shown in FIG. 3(d), a pair of contactors 31 a, 31 b is disposed back to back to eachother with respective protrusion facing outwardly and is fitted into athorough hole of an electrically insulating substrate 32 with a hollowring 39 therebetween. The hollow ring 39 ensures a space for theadjacent contactors 31 a, 31 b to make a stroke and prevents thecontactors from contacting each other even when they are deformed.

The socket for inspection shown in FIG. 3( d) is interposed between asemiconductor 35 and a transformer 38 of the measuring device for use.By being interposed between semiconductor 35 and transformer 38, thesocket is connected to an electrode 36 of semiconductor 35 and anelectrode 37 of transformer 38 with an appropriate contact load due tourging force of the spring. Accordingly, an electrical signal obtainedfrom semiconductor 35 is led to the measuring device through transformer38.

The micro terminal according to the present invention is useful as amicro terminal of a socket for inspection for semiconductor in land gridarray arrangement and the like. Further, the micro terminal according tothe present invention is useful as a micro terminal of a connector foran electronic device mounted on a land electrode of a communicationdevice such as a mobile phone or an electronic device such as a personalcomputer. Preferably, an electrode of an inspection device or anelectronic device is planar to obtain a secure connection with acontactor having a protrusion. However, an electrode having a convex orconcave portion or a recess can be used as well.

FIG. 9( c) shows another example of a contact sheet of a socket forinspection and a connector for installation or the like. As shown inFIG. 9( c), the contact sheet includes a micro terminal 91 according tothe present invention and has a hollow electrode 91 b penetrating asheet 92 in the thickness direction and contactors 91 a, 91 c on hollowelectrode 91 b. Hollow electrode 91 b has a hollow portion such that aspring of contactors 91 a, 91 c can make a stroke. In the example shownin FIG. 9( c), there is a pair of contactors 91 a, 91 c on and underhollow electrode 91 b. Although micro terminal 91 has a contactor onboth ends in contact with an electrode, a terminal having a contactor onone surface only is also effective and both are included in the presentinvention. In the example shown in FIG. 9( c), since the protrusion ofcontactors 91 a, 91 c has a V-shaped groove structure, a solder bumpelectrode of lower height is preferable as an electrode for connection.Thus, the micro terminal according to the present invention is widelyapplicable since specifications of a contactor can be changed inaccordance with a type of an electrode for connection.

(Method of Fabricating a Micro Terminal)

A method of fabricating a micro terminal according to the presentinvention is characterized in that a contactor in the micro terminal isfabricated by a method including the steps of: forming a resin mold byX-ray lithography; forming a layer including a metal material at theresin mold on an electrically conductive substrate by electroforming;polishing or grinding; forming a resin mold on the metal material layerby lithography; electroforming a layer including a metal material at theresin mold to form a protrusion protruding outwardly; removing the resinmolds; and removing the electrically conductive substrate.

Since a spring portion constituting the contactor is fabricated by amethod combining X ray and electroforming, higher aspect ratio can beobtained compared to lithography using UV, laser processing, etching orpunching. For example, a spring with aspect ratio (b/a) of at least 2shown in FIG. 1 can be easily fabricated and a spring with aspect ratioof at least 30 can be also fabricated. Due to high aspect ratio, a widtha of the spring can be made smaller and the number of spirals can bemade larger to provide a larger stroke. A thickness b of the spring canbe made larger to make contact load larger. Thus, a micro terminalhaving high connection reliability can be fabricated.

More specifically, a micro terminal with a stroke of at least 100 μm anda contact load of 0.03N can be easily fabricated. A contact load of atleast 0.1N can be also achieved. Thickness b can be made larger evenwhen width a of the spring is small, so that large current of at least0.5 A can be conducted.

In the present embodiment, a columnar spring portion is fabricated usingX ray (of a wavelength of 0.4 nm) with a shorter wavelength than UV (ofa wavelength of 200 nm), since high aspect ratio can be obtained.Preferably, X ray of highly directional synchrotron radiation(hereinafter referred to as “SR light”) is used. With LIGA (LithographieGalvanoformung Abformung) process using SR light, deep lithography ispossible and a metal micro structure of several hundreds of μm in heightcan be fabricated accurately in the order of a micron and in largeamount.

When a micro terminal is fabricated by mechanical processing by windingup a plate-shaped body for example, there is a limit in making the microterminal smaller. The micro terminal is 1000 μm in thickness b and500–1000 μm in diameter D even when it is smallest. With the microterminal of this size, it is difficult to address semiconductorinstalled in higher density. Further, it is difficult to fabricate aprecise micro terminal accurately with high reproducibility in largeamount. For the present invention, a micro terminal of 100–500 μm inthickness b and 100–1000 μm in diameter D can be fabricated precisely,accurately and with high reproducibility, so that it is possible toaddress densification of an electronic device. Due to a fabricationmethod combining lithography and electroforming, a micro structure canbe integrally formed, reducing the number of parts, parts cost andassembly cost.

Since the protrusion in contact with an electrode is formed by a methodcombining lithography and electroforming, the protrusion can be formedmore easily compared to a method of performing mechanical convexprocessing after forming a spring, leading to high productivity and highproduct yield. The protrusion can be formed accurately, so thatvariation in height of a terminal can be reduced. Compared tofabrication by mechanical processing, variation in stroke and contactload can be reduced to around one tenth, providing high connectionreliability.

FIG. 4 shows a fabrication method according to the present invention. Asshown in FIG. 4( a), a resin layer 42 is formed on an electricallyconductive substrate 41. For example, a metal substrate includingcopper, nickel, stainless steel or the like, or a silicon substratesputtered with a metal material such as titanium or chromium or the likeis used as the electrically conductive substrate. As the resin layer, aresin material mainly including poly methacrylate such as polymetylmethacrylate (PMMA), or a chemically amplified resin material sensitiveto X ray is used. The thickness of the resin layer can be freely set inaccordance with the thickness of a spring portion of a micro terminal tobe formed and can be set to 100 μm–500 mm, for example.

Then, a mask 43 is disposed on a resin material 42 and X ray 44 isapplied through mask 43. As the X ray, SR light is preferable. Mask 43includes a X ray absorbing layer 43 a and a light penetrable substrate43 b formed in accordance with a pattern of a spring portion of acontactor. Silicon nitride, silicon, diamond, titanium or the like isused for light penetrable substrate 43 b. For X ray absorbing layer 43a, a heavy metal such as gold, tungsten, tantalum or a compound thereofis used. Of resin layer 42, a resin layer 42 a is exposed and modifiedby the application of X ray 44, while a resin layer 42 b is not exposeddue to X ray absorbing layer 43 a. Accordingly, only a portion 42 amodified by X ray 44 is removed by development to obtain a resin mold 42b shown in FIG. 4( b).

Then, electroforming is performed to deposit a metal material 45 atresin mold 42 b, as shown in FIG. 4( c). Electroforming means to form alayer including a metal material on an electrically conductive layerusing a metal ion solution. By electroforming using electricallyconductive substrate 41 as a plating electrode, metal material 45 can bedeposited at resin mold 42 b. When the metal material is deposited toalmost fill a vacancy portion of the resin mold, a spring can beobtained from the deposited metal material layer. When the metalmaterial is deposited higher than the height of the resin mold and overthe resin mold, a metal micro structure having a vacancy portion can beobtained by removing the resin mold and the substrate. The structureobtained can be effectively used as a metal mold in a fabrication methodaccording to the present invention using a metal mold as describedbelow. Although nickel, copper or an alloy thereof is used for the metalmaterial, for example, nickel or a nickel alloy such as nickel-manganeseis preferable to increase resistance to wear.

After electroforming, a predetermined thickness is obtained by polishingor grinding (FIG. 4( d)). Then, a resin layer 46 including a negativeresist, for example, is formed on the spring (FIG. 4( e)). When UV 47 orX ray is applied through mask 48, of resin layer 46, a resin layer 46 bis exposed, while a resin layer 46 a is not exposed (FIG. 4( f)).Accordingly, when a portion cured by UV or the like is left and otherportion is removed by development, a resin mold 46 b is obtained (FIG.4( g)). For mask 48, a mask of specifications similar to mask 43 can beused.

Then, a layer including a metal material is electroformed at resin mold46 b and the plating is grown to form a protrusion 49 protrudingoutwardly. As shown in FIG. 4( h), protrusion 49 has a contact surfacewith an electrode forming a part of a paraboloid of revolution. Aprotrusion having a contact surface forming a part of a sphere (notshown) can be also formed. In electroforming, lines of electric forceare extended in the vacancy portion of resin mold 46 b and equivalentpoints of electric force form a sphere or a paraboloid of revolution.Accordingly, when the plating is grown, the surface of the plating caneasily form a protrusion that is a part of a sphere or a paraboloid ofrevolution.

After protrusion 49 is formed, resin molds 42 b, 46 b are removed by wetetching or plasma ashing (FIG. 4( i)), and then electrically conductivesubstrate 41 is removed by wet etching using an acid or alkali ormechanically to obtain a contactor having a columnar spring 45 andprotrusion 49 according to the present invention shown in FIG. 4( j). Inorder to increase conductivity with an electrode of an electronic deviceand the like, preferably, a micro terminal including the obtainedcontactor is provided with a coat layer of 0.05–1 μm in thickness formedby barrel plating which includes a precious metal such as Au, Rh, Ag,Ru, Pt, Pd or the like, or an alloy of a precious metal such aspalladium-cobalt, or polytetrafluoroethylene gold. A coat layer ofpolytetrafluoroethylene gold can be formed by composite plating ofpolytetrafluoroethylene and gold. The coat layer can be also formed in aprocess before a substrate is removed (FIG. 1( i)).

On the protrusion formed at the central portion of the contactor, asshown in FIG. 8, for example, a V-shaped groove can be formed by cuttingwith a dicer. First, a rotary teeth 85 of a dicer rotating in adirection shown by an arrow (b) is applied to an end of a protrusion 89of a contactor 80 shown in (a) and then the dicer is moved in adirection orthogonal to the plane of FIG. 8 to form a V-shaped groove onthe end of protrusion 89. As shown in (c), if necessary, by applying therotary teeth of the dicer to the end of the protrusion in a differentdirection repeatedly and moving the dicer as shown by the arrow, theprotrusion can be cut similarly. The groove forming can be performedafter forming of a protrusion, before or after removing the resin molds,or before or after removing the electrically conductive substrate. Thecontactor according to the present invention can be fabricated on asubstrate at one time in large number. Accordingly, the contactor can beproduced in large amount by dicing the contactor formed on thesubstrate, reducing manufacturing cost.

FIG. 3 shows a method of fabricating a socket for inspection from thecontactor obtained. A connector for installation can be fabricatedsimilarly. The method of fabricating a socket for inspection or aconnector for installation is not limited to the method shown in FIG. 3,however, the method shown in the FIG. 3 is preferable since fabricationis easy. First, as shown in FIG. 3( a), a through hole is formed on anelectrically insulating substrate 32 in accordance with a position of anelectrode of semiconductor to be inspected. The size of the through holeis adapted to the outer diameter of a micro terminal to be accommodated.Then, an electrically insulating lower lid sheet 33 similarly formedwith a through hole in accordance with an arrangement of an electrode ofsemiconductor is adhered to substrate 32. The size of the through holeof the lower lid sheet is made smaller than the outer diameter of amicro terminal to be accommodated to prevent the micro terminal frombeing detached from the substrate.

Then, as shown in FIG. 3( b), a pair of contactors 31 a, 31 b orientedback to back with the protrusion of contactor 31 facing outwardly andhaving a hollow ring 39 interposed therebetween is fitted into thethrough hole on substrate 32. Then, an upper lid sheet 34 similar tolower lid sheet 33 is adhered to substrate 32 to fix contactor 31 andhollow ring 39, and a socket for inspection according to the presentinvention is obtained. Material for substrate 32, lower lid sheet 33 andupper lid sheet 34 can be selected arbitrarily from an electricallyinsulating material such as polyimide resin, commonly used fiberreinforced resin (FRP) or the like.

FIG. 9 shows another method of fabricating a contact sheet of a socketfor inspection or a connector for installation or the like. First, asshown in (a), a through hole is formed on a sheet 92 in accordance witha position of an electrode to be connected. Then, a through electrode 91b is fitted into sheet 92. As shown in (b), a pair of contactorsoriented back to back with the protrusion of contactors 91 a, 91 cfacing outwardly is then joined to hollow electrode 91 b to obtain acontact sheet according to the present invention shown in (c).

Preferably, the hollow electrode and the contactor are joined byresistance welding. When using resistance welding, it is not necessaryto consider the flow of molten solder and the pitch of micro terminalscan be made narrower, compared to when using joining by solder. Sincemechanical strength of the joined portion is larger and resistance toheat and a chemical agent is higher compared to soldering, longerlifetime is provided. Further, higher accuracy can be obtained sincethere is no deviation in position due to deformation of a middle layerand stress as occurs when soldering is used.

For sheet 92, polyimide resin, commonly used fiber reinforced resin(FRP) or the like can be used. Micro terminal 91 according to theprevent invention is a micro structure with an outer diameter of notmore than 1 mm. Since fabrication by the methods shown in FIGS. 3 and 9is easy, a micro terminal according to the present invention can befabricated easily, efficiently and at lower cost by performing punchingprocessing in broken lines 94 a, 94 b once a contact sheet shown in FIG.9( c) is formed.

Another method of fabricating a micro terminal according to the presentinvention is characterized in that a contactor in the micro terminal isfabricated by a method including the steps of: forming a resin mold by ametal mold; forming a layer including a metal material at the resin moldon an electrically conductive substrate by electroforming, polishing orgrinding; forming a resin mold on the layer including a metal materialby lithography; electroforming a layer including a metal material at theresin mold to form a protrusion protruding outwardly; removing the resinmolds; and removing the electrically conductive substrate. With thismethod also, similarly to the above-described fabrication method offorming a contactor by X-ray lithography, the micro terminal can befabricated accurately with high reproducibility. Since the fabricatedcontactor has high aspect ratio and the central protrusion can be formedaccurately, contact reliability is high. Further, advantageously, thecontactor can be fabricated in large amount using the same metal mold.

As shown in FIG. 5( a), a metal mold 50 having a convex portion is usedto form a concave resin mold 52 by molding such as press or injectionmolding. For resin, a thermoplastic resin such as acrylic resin likepolymetyl methacrylate, polyurethane resin, polyacetal resin likepolyoxy methylene is used. Preferably, metal mold 50 is fabricated bythe above-describe method combining X-ray lithography andelectroforming, since the metal mold is a metal micro structure similarto the micro terminal according to the present invention.

After turned upside down, resin mold 52 is adhered to an electricallyconductive substrate 51, as shown in FIG. 5( c). Then, as shown in FIG.5( d), resin mold 52 is polished to form a resin mold 52 b. After that,similarly to the above, a metal material 55 is deposited at resin mold52 b by electroforming (FIG. 5( e)), a uniform thickness is provided bypolishing or grinding (FIG. 5( f)), a resin layer 56 is formed (FIG. 5(g)), and UV 57 or X ray is applied through a mask 58. Of resin layer 56,resin layer 56 b is exposed while a resin layer 56 a is not (FIG. 5(h)), so that a resin mold 56 b can be obtained by leaving a portioncured by UV or the like by development and removing other portion (FIG.5( i)).

Then, by electroforming to grow the plating, a protrusion 59 shown inFIG. 5 (j) having a contact surface with an electrode being a part of aparaboloid of revolution or the like is formed. After protrusion 59 isformed, by removing resin molds 52 b, 56 b (FIG. 5( k)) and removingelectrically conductive substrate 51, a contactor having a columnarmetal material 55 and protrusion 59 can be fabricated (FIG. 5( l)).Preferably, the micro terminal is provided with a coat layer by Au, Rhor an alloy thereof or the like.

EXAMPLE 1

As shown in FIG. 4( a), resin layer 42 was formed on electricallyconductive substrate 41. For the electrically conductive layer, asilicon substrate sputtered with titanium was used. The resin layer wasformed by copolymer of methyl methacrylate and methacrylate. Thethickness of the resin layer was 200 μm.

Then, mask 43 is disposed on resin layer 42 and X ray 44 was applied viamask 43. X ray was SR light. For mask 43, a light penetrable substrate43 b with a X ray absorbing layer 43 a including tungsten nitride formedthereon was used. X ray absorbing layer 43 a was formed in accordancewith a pattern of a contactor.

After the application of X ray 44, development was performed with methylisobutyl ketone and a portion 42 a modified by X ray 44 was removed toobtain resin mold 42 b shown in FIG. 4( b). Then, by electroforming, asshown in FIG. 4( c), metal material 45 was deposited at a vacancyportion of resin mold 42 b. For the metal material, nickel was used.

After electroforming, an uneven portion on the surface was removed bypolishing to provide a uniform thickness (FIG. 4( d)). Then, resin layer46 was formed (FIG. 4( e)) and UV47 was applied via mask 48 (FIG. 4(f)). A UV resist (SU-8 manufactured by Micro Chemical Corporation) wasused for resin layer 46. The thickness of resin layer 46 was 50 μm. Acommonly used photo-mask was used for mask 48. Then, a portion exceptfor a portion cured by the UV application was removed by development toobtain resin mold 46 b having a hole in its center (FIG. 4( g)).

Then, by electroforming to grow the plating metal to the height of 50 μmabove the top surface of resin mold 46 b, protrusion 49 protrudingoutwardly was formed (FIG. 4( h)). After protrusion 49 was formed, resinmolds 42 b, 46 b were removed by plasma ashing (FIG. 4( i)), and acontactor with a protrusion was mechanically detached from electricallyconductive substrate 41 (FIG. 4( j)). Then, a coat layer (not shown)including gold of 0.1 μm in thickness was formed by barrel plating. Thecontactor may be detached from the substrate by etching the electricallyconductive substrate. The total height of the protrusion formed on thespring was 100 μm.

FIG. 1 shows the obtained contactor. The contactor had columnar spring 1u and protrusion 1 t protruding outwardly at center 1 uc of spring 1 u.Protrusion 1 t included a contact surface 1 tc with an electrode andcontact surface 1 t was a part of a paraboloid of revolution in shape.Spring 1 u had perimeter portion 1 ug having a tubular ring structureand was 480 μm in diameter D. The thickness b of the spring was 150 μmand the width a of the spring was 10 μm and the aspect ratio (b/a) was15. The number of spirals was 3.3 and a stroke was 100 μm. At thecentral portion of the spiral spring was a protrusion with a neck andhaving a height c of 100 μm.

As shown in FIG. 3( a), substrate 32 and lower lid sheet 33 formed witha through hole respectively were adhered at the position of an electrodeof semiconductor to be inspected. For substrate 32, a substrate formedof polyimide resin and 500 μm in thickness was used and a through holeof 500 μm in diameter was provided. For lower lid sheet 33, a sheetformed of polyimide resin and 20 μm in thickness was used and a hole of400 μm in diameter was formed in accordance with the position of thethrough hole of substrate 32.

As shown in FIG. 3( b), contactors 31 a, 31 b oriented back to back withthe protrusion facing outwardly and having hollow ring 39 of 480 μm inouter diameter and 200 μm in height interposed therebetween were fittedinto the through hole of substrate 32. Then, lower lid sheet 33 andsimilar upper lid sheet 34 were adhered to substrate 32 to obtain asocket for inspection according to the present invention shown in FIG.3( c).

As shown in FIG. 3( d), the obtained socket for inspection was mountedon electrode 37 of transformer 38 of an inspection device. Semiconductor35 as a body to be inspected was disposed on the inspection device andwas applied pressure with a force of 70 mN in the direction shown by thearrow. Then, due to urging force of the spring, electrical conductionwas obtained between planar electrode 36 of semiconductor 35 andelectrode 37 of transformer 38 and inspection of semiconductor could beperformed based on the obtained electrical signal.

Although diameter D of the micro terminal was 480 μm in the presentexample, a micro terminal of around 100 μm in diameter D can be alsofabricated by the method according to the present invention. Therefore,it was found that higher density installation of electronic devicescould be addressed.

It should be understood that the embodiments and examples disclosedherein are illustrative and non-restrictive in every respect. The scopeof the present invention is defined by the terms of the claims, ratherthan the description above, and is intended to include any modificationswithin the scope and meaning equivalent to the terms of the claims.

INDUSTRIAL APPLICABILITY

With the present invention, a socket for inspection and a connector forinstallation including a micro terminal with high connection reliabilitycan be provided.

1. A micro terminal with electrical conduction between said micro terminal and an electrode of an electronic device or an inspection device, comprising a columnar contactor in contact with the electrode, wherein said contactor has a plate-shaped spring structure that is elastically deformed by being pressed against the electrode, a perimeter portion of said spring structure has a tubular ring structure, and said contactor has a protrusion protruding outwardly at its end in contact with the electrode, and said protrusion is shaped to have a part of a sphere or a paraboloid of revolution.
 2. The micro terminal according to claim 1, wherein said contactor has a spiral spring structure.
 3. The micro terminal according to claim 1, wherein said micro terminal has said contactor at each of opposing ends in contact with the electrode.
 4. The micro terminal according to claim 1, wherein said protrusion has a V-shaped groove opening toward the direction in which said protrusion protrudes.
 5. The micro terminal according to claim 1, wherein said micro terminal includes nickel or a nickel alloy.
 6. The micro terminal according to claim 1, wherein said micro terminal has a coat layer including a precious metal or an alloy of a precious metal or polytetrafluoroethylene gold.
 7. A contact sheet including the micro terminal according to claim 1, having a hollow electrode penetrating the sheet in a thickness direction and said contactor on said hollow electrode, wherein said hollow electrode has a hollow portion for a spring of said contactor to make a stroke.
 8. The contact sheet according to claim 7, wherein said hollow electrode and said contactor are joined by resistance welding.
 9. A socket for inspection including the micro terminal according to claim 1, wherein said socket is used for inspection of semiconductor in land grid array arrangement.
 10. An inspection device including the socket according to claim
 9. 11. A method of inspecting semiconductor using the socket according to claim
 9. 12. A connector for installation including the micro terminal according to claim 1, wherein said connector is connected to a land electrode.
 13. An electronic device including the connector according to claim
 12. 